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Mmmmmm....stat pie


OK, the new Basketball Prospectus page is unspeakably cool.  Take a look-see at some of the new things it offers:

The first three columns reflect a player's offensive usage and production: oPOSS is an estimate of the raw number of possessions used on the offensive end by each player. The formula is the same as the one used to calculate team possessions (see below) except that in each game, the total number of individual possessions is brought into balance with the team possessions using a multiplier. PC is an estimate of points created by the player. Points created in NBAPET tabulates only "positive" contributions, ie., making a shot, getting to the foul line, grabbing a rebound, etc. The value of each category varies somewhat from year to year because the value of a possession changes a little each season. Points lost (PL) is an estimate of offensive efficiency, depending on the league-wide value of a possession. (PC-(oPOSS * league Pts/Poss)). Thus, the lower the points-lost total, the more efficient a player is. Zero is exactly average. Soon to be added to the table will be PC100, or points created per 100 possessions (PC / oPOSS * 100).

The next three columns are an attempt to quantify a player's defensive contributions. In each box score, NBAPET "charges" each player for the offensive production from his most likely counterpart. In general, starting point guards are matched up with opposing starting point guards, etc., though an effort is made to capture cross-matchups. Also, these figures are affected by playing time. Thus if Dwight Howard is matched with Kendrick Perkins and Howard plays 39 minutes and Perkins 21, Perkins' defensive totals will reflect just 21 minutes' worth of Howard's production. The final 18 minutes are distributed among Orlando's reserve interior defenders. dPOSS is an estimate of a player's defensive possessions used on the season. Points against (PA) would be more accurately described as "points created against" and uses the same methodology as points created. Points saved (PS) is the counterpart to points lost. Thus, it is an aggregate total reflecting a player's defensive efficiency as compared to league average. The higher the total, the better. Zero is exactly average. Soon to be added to the table will be PA100, or points allowed per 100 possessions (PA / dPOSS * 100).

Two more defensive metrics follow. First is dMULT, or defensive multiplier. This measures how effectively a player has limited his counterparts' efficiency on a per-possession basis compared to their season rate. Thus, if Ron Artest has a dMULT of .950, that says Artest has held his counterparts to 95% of their normal production on a per possession basis. dQUAL (defensive counterpart quality) is a strength-of-opponent measure. It calculates the composite season points created per possession figures for all of a player's box score counterparts and compares it to the league average. A dQUAL total of 1.08 means that the player's counterparts have been eight percent better than league average.

Finally, the last three columns reflect the meat of the NBAPET player rating system. The aggregate offensive and defensive points created, saved and lost are combined to calculate the number of wins a player is responsible for. The raw total is WP, or wins produced. WP82 is wins produced prorated for the full 82-game season. However a player's availability is reflected in this total. Thus if a player has missed 50% of his team's games, his WP82 figure will reflect this--it isn't "wins produced per 82 games." WP3K, however, removes all playing time and availability differences. It's simply wins produced per 3000 minutes.

Here's how those measurements play out with Kevin Love and Big Al:

Big Piranha Big Al
oPoss 255 771
PC 370 826
PL -91 21
dPoss 223 507
PA 254 638
PS -9 -81
dMult 0.775 1.041
dQual 0.860 1.006
WP 1.6 2.3
WP82 3.2 4.7
WP3K 5.2 4.7

I can't wait until the PA/PC100 are added.  You can already play around with this a bit to find out that Love creates 1.45 favorable things/oPoss compared to Big Al's 1.07.  I think that would be a useful stat.  It's pretty much one of the main indicators that I have been using in Hoopus' draft board (i.e. favorably ended/extended possessions). Love isn't all that efficient of a defensive player but he's close to average and he holds the competition below their normal production.  If the Big Piranha ever figures out how to finish near the rim, and if Big Al ever figures out how to be an average defender, the Wolves are going to be on to something.  The thought of a 20 year old rookie putting up these kinds of numbers with some pretty glaring areas of improvement still on the board...well, let's keep our fingers crossed.